Have been getting a squealing noise on my S3 BAM the last couple of weeks. The boost builds up then the squealing/shrieking starts,usually when you've got the car under load or planting your foot. Got a my vag mechanic friend to take a peek and he suggested change the dv valve which I did this morning with a forge item but on the test drive the noise was still there,maybe not as noisy but still present. I've had a poke around at top of engine and no pipes seem loose. The only time I've heard anything like this was on my seat leon fr 170bhp when the cambelt tensioner was failing at 20k miles,but with a slightly different noise. My cambelt was changed 30k ago so don't really want to go that route on a hunch. Any suggestions would be appreciated.